二氧化保护是一种（）保护的焊接方法A、气B、渣C、气渣联合D、以上都不是

下面的图形没有办法求出周长的是[ ]

A．长方形

B．三角形

C．多边形

D．球体

Parents often believe that they have a good relationship with their teenagers (青少年). But last summer, Joanna and Henry noticed a change in their older son: suddenly he seemed to be talking far more to his friends than to his parents . “The door to his room is always shut.” Joanna noted.

Tina and Mark noticed similar changes in their 14-year-old daughter. “She used to cuddle up (蜷伏)with me on the sofa and talk ,” said Mark . “Now we joke that she does this only when she wants something. Sometimes she wants to be treated like a little girl and sometimes like a young lady. The problem is figuring out which time is which.”

Before age 11, children like to tell their parents what’s on their minds. “In fact, parents are first on the list.” said Michael Riera, author of Uncommon Sense for Parents with Teenagers. “This completely changes during the teen years.” Riera explained. “They talk to their friends first, then maybe their teachers, and their parents last.”

Parents who know what’s going on in their teenagers’ lives are in the best position to help them. To break down the wall of silence, parents should create chances to understand what their children want to say, and try to find ways to talk and write to them. And they must give their children a mental break, for children also need freedom, though young. Another thing parents should remember is that to be a friend, not a manager, with their children is a better way to know them.

69. “The door to his room is always shut” suggests that the son        .

A. is always busy with his studies           B. doesn’t want to be disturbed

C. keeps himself away from his parents       D. begins to dislike his parents

70. What troubles Tina and Mark most is that        .

A. their daughter isn’t as lovely as before   B. they can’t read their daughter’s mind exactly

C. they don’t know what to say to their daughter

D. their daughter talks with them only when she needs help

71. Which of the following best explains “the wall of silence” in the last paragraph?

A. Teenagers talk a lot with their friends.      

B. Teenagers do not want to understand their parents.

C. Teenagers do not talk much with their parents.

D. Teenagers talk little about their own lives.

72. What can be learned from the passage?

A. Parents are unhappy with their growing children.

B. Parents have suitable ways to talk with their teenagers.

C. Parents should be patient with their silent teenagers.

D. Parents should try to understand their teenagers.

某企业新接到一张JC208型号产品1800台的订单，为完成经营任务，首先要选择主要供应单位，因时间紧迫，企业采购部门改变通常采用的招标方法，改为协商选择，就是根据了解的情况，选出供应条件较好的几个供应单位，同他们分别进行协商，在此基础上确定合适的供应者。

协商选择还可以应用于( )。

A．供应市场竞争不激烈时

B．采购商品技术规格复杂的情况

C．更关注价格因素

D．不是关键的采购物品

成都解放于什么时间（）

A.1949.5

B.1949.8

C.1949.12

D.1950.1

If interest rates fall, the:（）

A. callable bond’s price rises faster than that of a noncallable but otherwise identical bond.

B. callable bond’s price rises more slowly than that of a noncallable but otherwise identical bond.

C. value of call option embedded in the callable bond fails.